430 General Notes. [April, 
In seeking light upon the primordial condition of the Vertebrata, 
says the author, one naturally looks to such forms as the Myxi- 
noids. For in these types, even in the adult state, there are 
neither limbs nor vertebra, and no distinction between head and 
body, except the beginning in the head, of a cartilaginous skull; 
a continuous structure—not showing the least sign of se 
segmentation, and by far the greater part of which is in front of 
the notochord, or axis of the organism. But here our gr 
work agrees with the developmental, for the continuous skull-bats 
constantly arise before the secondary cartilaginous that are found 
between the myotomes behind the head. Evidently, therefore 
the early “ Craniata” grew supports to the enlarged and subd 
vided front end of their neural axis, long before anything beyond 
strong fibrous septa developed between the muscular segments 
of the body. As for the linear growth, the greater or less extet- 
sion backwards of the main organs—circulatory, respirator 
digestive, urogenital—that, in the evolution of the primary form, 
was a thing to be determined by the *“ surroundings” of the bh: 
“ Thereafter as sey may be” was the tentative idea in ane 
“Certainly in the Marsipobranchs and in their relations, 8° 
larval ‘ Anura; we have the most archaic ‘ Craniata’ now en 
in these the organs may be extended far backwards in a vermi i 
creature, as in these low fishes, or kept well swung bea 
head—the body and tail together forming merely a ee J 
organ, as is seen in tadpoles, especially the gigantic tadpo 
Pseudis. ‘t 
necessity 
vesicular brain, the suctorial lips, the branchial epi a 
special organs of sense—these all call for soppa be M yé 
noids we find that four special modifications of the p 
tissue series are developed for the support of the propery putare 
organs, and for them only; thus these fishes are Crane i 
not Vertebrata ; that is, if we stick to the letter, whi 
we do not. ful study o 
“At first some disappointment is felt, after Oe ht y fe 
these types, for, notwithstanding the low w m hes e sate 
main, they are mere specialized Ammocætes, we their gms 
nd 
nsformation, 
theip 
4 wi esi 
habits of Jife as any Vertebrates whatever, the highest we 
“ Yet, on the whole, the Myxinoides are a sort of Am o es 
type, whilst the transformed Ammoccete, the larval lamprey But thè 
nearest to the untransformed frog or toad—the ta he Joses th 
mere putting of this show (suggests at any rate) wa 
fauna of the world has sustained during the evolution 
